The human heart is divided into four compartments or chambers. The left and right atria are located in the upper portion of the heart and the left and right ventricles are located in the lower portion of the heart. The left and right atria are separated from each other by a muscular wall, the interatrial septum, while the ventricles are separated by the interventricular septum.
Either congenitally or by acquisition, abnormal openings, holes, or shunts can occur between the chambers of the heart or between the great vessels, causing blood to flow along an anomalous pathway therethrough. Such deformities are usually congenital and originate during fetal life when the heart forms from a folded tube into a four chambered, two unit system. The deformities result from the incomplete formation of the septum, or muscular wall, between the chambers of the heart and can cause significant problems. Ultimately, the deformities add strain on the heart, which may result in heart failure if they are not corrected.
One such deformity or defect, a patent foramen ovale (PFO), is a persistent, one-way, usually flap-like opening in the wall between the right atrium and left atrium of the heart. Since left atrial pressure is normally higher than right atrial pressure, the flap typically stays closed. Under certain conditions, however, right atrial pressure exceeds left atrial pressure, creating the possibility for right to left shunting that can allow blood clots to enter the systemic circulation. This is particularly worrisome to patients who are prone to forming venous thrombi, such as those with deep vein thrombosis or clotting abnormalities.
Nonsurgical (i.e., percutaneous) closure of a PFO, as well as similar intracardiac defects such as an atrial septal defect, a ventricular septal defect, and closure of the left atrial appendage, is possible using a variety of mechanical closure devices. These percutaneously, transvascularly introduced devices, which avoid the potential side effects often associated with standard anticoagulation therapy of a patient having one of these defects, typically consist of a metallic structural framework that is combined with a synthetic or biological tissue scaffold material applied to the structural framework.
The structural framework of the prior art intracardiac occluders are often stiff and rigid, lacking the flexibility necessary to conform with irregularly shaped intracardiac defects. This results in trauma to surrounding tissues, chronic inflammation, residual leaks, and even breakage of the occluder, impairing closure of the defect to which the intracardiac occluder is applied.